This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The proposed XAS experiments are part of a project designed to examine how nature designs proteins to recognize one metal (or small group of metals) from all the metals present in cells, and generate specific biological responses. Proteins involved in nickel trafficking in E. coli and H. pylori were chosen because of the desire to examine an entire trafficking system (simplicity of the nickel traffic pattern) in order to understand the general features of specific metal recognition, and because of the potential for antibiotic strategies involving interference with bacterial nickel trafficking. XAS provides the main structural tool for examining the structure of cognate and non-cognate metal ions bound to metallotransporters, metallochaperones, and metalloregulators.